Multi-speed transmission having four planetary gear sets for producing at least eight gear speeds

ABSTRACT

A transmission of the present invention has an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices may include clutches and brakes. The torque transmitting devices are selectively engageable in combinations of at least two to establish at least eight forward speed ratios and at least one reverse speed ratio.

FIELD

The invention relates generally to a multiple speed transmission havinga plurality of planetary gear sets and a plurality of torquetransmitting devices, and more particularly to a transmission havingeight or more speeds, four planetary gear sets and a plurality of torquetransmitting devices.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission uses a combination of frictionclutches or brakes, planetary gear arrangements and fixedinterconnections to achieve a plurality of gear ratios. The number andphysical arrangement of the planetary gear sets, generally, are dictatedby packaging, cost and desired speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needfor an improved, cost-effective, compact multiple speed transmission.

SUMMARY

A transmission is provided having an input member, an output member,four planetary gear sets, a plurality of coupling members and aplurality of torque transmitting devices. Each of the planetary gearsets includes first, second and third members. The torque transmittingdevices are for example clutches and brakes.

In an aspect of the present invention a transmission is provided havingan input member, an output member, a first, second, third and fourthplanetary gear sets each having sun gears, carrier members and ringgears. The input member is continuously interconnected with the sun gearof the first planetary gear set and the sun gear of the third planetarygear set. The output member is selectively interconnected with the ringgear of the fourth planetary gear set.

Additionally, a first interconnecting member continuously interconnectsthe sun gear of the first planetary gear set with sun gear of the thirdplanetary gear set, a second interconnecting member continuouslyinterconnects the carrier member of the first planetary gear set withthe carrier member of the second planetary gear set, a thirdinterconnecting member continuously interconnects the ring gear of thefirst planetary gear set with the ring gear of the second planetary gearset, a fourth interconnecting member continuously interconnects the sungear of the second planetary gear set with the carrier member of thethird planetary gear set and a fifth interconnecting member continuouslyinterconnects the ring gear of the third planetary gear set with the sungear of the fourth planetary gear set.

Further, a first torque transmitting device is selectively engageable tointerconnect the input member, sun gear of the first planetary gear setand the sun gear of the third planetary gear set with the carrier memberof the fourth planetary gear set, a second torque transmitting device isselectively engageable to interconnect the sun gear of the secondplanetary gear set and the carrier member of the third planetary gearset with the carrier member of the fourth planetary gear set, a thirdtorque transmitting device is selectively engageable to interconnect thecarrier member of the first planetary gear set and carrier member of thesecond planetary gear set with the stationary member, a fourth torquetransmitting device is selectively engageable to interconnect the ringgear of the first planetary gear set and the ring gear of the secondplanetary gear set with the stationary member, a fifth torquetransmitting device is selectively engageable to interconnect the ringgear of the third planetary gear set and the sun of the fourth planetarygear set with the stationary member, and a sixth torque transmittingdevice is selectively engageable to interconnect the carrier member ofthe fourth planetary gear set with the stationary member. The torquetransmitting devices are selectively engageable in combinations of atleast two to establish at least eight forward speed ratios and at leastone reverse speed ratio between the input member and the output member.

It is thus an object of the present invention to provide a transmissionhaving four planetary gear sets.

It is a further object of the present invention to provide atransmission having eight forward speeds and at least one reverse.

It is a still further object of the present invention to provide atransmission having four planetary gear sets, a plurality of couplingmembers and a plurality of torque transmitting devices.

Further objects, aspects and advantages of the present invention willbecome apparent by reference to the following description and appendeddrawings wherein like reference numbers refer to the same component,element or feature.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a lever diagram of an embodiment of a eight speed transmissionaccording to the present invention;

FIG. 2 is a diagrammatic view of an embodiment of a eight speedtransmission according to the present invention; and

FIG. 3 is a truth table presenting the state of engagement of thevarious torque transmitting elements in each of the available forwardand reverse speeds or gear ratios of the transmission illustrated inFIGS. 1 and 2.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that in the particular exampleprovided, the eight speed automatic transmission of the presentinvention has an arrangement of permanent mechanical connections betweenthe elements of the four planetary gear sets. A first component orelement of a first planetary gear set is permanently coupled to a firstcomponent or element of a third planetary gear set. A second componentor element of the first planetary gear set is permanently coupled to asecond component or element of a second planetary gear set. A thirdcomponent or element of the first planetary gear set is permanentlycoupled to a third component or element of the second planetary gearset. A first component or element of the second planetary gear set ispermanently coupled to a second component or element of a thirdplanetary gear set. Finally, the third component or element of the thirdplanetary gear set is also permanently coupled to a first component orelement of a fourth planetary gear set.

Referring now to FIG. 1, an embodiment of a eight speed transmission 10is illustrated in a lever diagram format. A lever diagram is a schematicrepresentation of the components of a mechanical device such as anautomatic transmission. Each individual lever represents a planetarygear set wherein the three basic mechanical components of the planetarygear set are each represented by a node. Therefore, a single levercontains three nodes: one for the sun gear, one for the planet gearcarrier, and one for the ring gear. The relative length between thenodes of each lever can be used to represent the ring-to-sun ratio ofeach respective gear set. These lever ratios, in turn, are used to varythe gear ratios of the transmission in order to achieve appropriateratios and ratio progression. Mechanical couplings or interconnectionsbetween the nodes of the various planetary gear sets are illustrated bythin, horizontal lines and torque transmitting devices such as clutchesand brakes are presented as interleaved fingers. If the device is abrake, one set of the fingers is grounded. Further explanation of theformat, purpose and use of lever diagrams can be found in SAE Paper810102, “The Lever Analogy: A New Tool in Transmission Analysis” byBenford and Leising which is hereby fully incorporated by reference.

The transmission 10 includes an input shaft or member 12, a firstplanetary gear set 14 having three nodes: a first node 14A, a secondnode 14B and a third node 14C, a second planetary gear set 16 havingthree nodes: a first node 16A, a second node 16B and a third node 16C, athird planetary gear set 18 having three nodes: a first node 18A, asecond node 18B and a third node 18C, a fourth planetary gear set 20having three nodes: a first node 20A, a second node 20B and a third node20C and an output shaft or member 22.

The input member 12 is coupled to the third node 14C of the firstplanetary gear set 14. The first node 14A of the first planetary gearset 14 is coupled to the first node 18A of the third planetary gear set18. The second node 14B of the first planetary gear set 14 is coupled tothe second node 16B of the second planetary gear set 16. The third node14C of the first planetary gear set 14 is coupled to the third node 16Cof the second planetary gear set 16. The first node 16A of the secondplanetary gear set 16 is coupled to the second node 18B of the thirdplanetary gear set 18. The third node 18C of the third planetary gearset 18 is coupled to the first node 20A of the fourth planetary gear set20. The output member 22 is coupled to the third node 20C of the fourthplanetary gear set 20.

A first clutch 26 selectively connects the first node 14A of the firstplanetary gear set 14 and the first node 18A of the third planetary gearset 18 with the second node 20B of the fourth planetary gear set 20. Asecond clutch 28 selectively connects the first node 16A of the secondplanetary gear set 16 and the second node 18B of the third planetarygear set 18 with the second node 20B of the fourth planetary gear set20. A first brake 30 selectively connects the second node 14B of thefirst planetary gear set 14 and the second node 16B of the secondplanetary gear set 16 with a stationary element or a transmissionhousing 50. A second brake 32 selectively connects the third node 14C ofthe first planetary gear set 14, the third node 16C of the secondplanetary gear set 16 with a stationary element or a transmissionhousing 50. A third brake 34 selectively connects the third node 18C ofthe third planetary gear set 18 with a stationary element or atransmission housing 50. A fourth brake 36 selectively connects thesecond node 20B of the fourth planetary gear set 20 with the stationaryelement or the transmission housing 50.

Referring now to FIG. 2, a stick diagram presents a schematic layout ofthe embodiment of the eight speed transmission 10 according to thepresent invention. In FIG. 2, the numbering from the lever diagram ofFIG. 1 is carried over. The clutches, brakes, and couplings arecorrespondingly presented whereas the nodes of the planetary gear setsnow appear as components of planetary gear sets such as sun gears, ringgears, planet gears and planet gear carriers.

For example, the planetary gear set 14 includes a sun gear member 14A, aring gear member 14C and a planet gear carrier member 14B that rotatablysupports a set of planet gears 14D (only one of which is shown). The sungear member 14A is connected for common rotation with the input shaft ormember 12. The ring gear member 14C is connected for common rotationwith a first shaft or interconnecting member 42. The planet carriermember 14B is connected for common rotation with a second shaft orinterconnecting member 44 and a third shaft or interconnecting member46. The planet gears 14D are each configured to intermesh with both thesun gear member 14A and the ring gear member 14C.

The planetary gear set 16 includes a sun gear member 16A, a ring gearmember 16C and a planet gear carrier member 16B that rotatably supportsa set of planet gears 16D (only one of which is shown). The sun gearmember 16A is connected for common rotation with a fourth shaft orinterconnecting member 48. The ring gear member 16C is connected forcommon rotation with the first shaft or interconnecting member 42. Theplanet carrier member 16B is connected for common rotation with thethird shaft or interconnecting member 46. The planet gears 16D are eachconfigured to intermesh with both the sun gear member 16A and the ringgear member 16C.

The planetary gear set 18 includes a sun gear member 18A, a ring gearmember 18C and a planet gear carrier member 18B that rotatably supportsa set of planet gears 18D (only one of which is shown). The set ofplanet gears 18D are each configured to intermesh with both the sun gearmember 18A and the ring gear member 18C. The sun gear member 18A isconnected for common rotation with the input shaft or member 12. Thering gear member 18C is connected for common rotation with a fifth shaftor interconnecting member 52. The planet carrier member 18B is connectedfor common rotation with the fourth shaft or interconnecting member 48and a sixth shaft or interconnecting member 54.

The planetary gear set 20 includes a sun gear member 20A, a ring gearmember 20B and a planet gear carrier member 20C that rotatably supportsa set of planet gears 20D (only one of which is shown). The sun gearmember 20A is connected for common rotation with the fifth shaft orinterconnecting member 52. The ring gear member 20C is connected forcommon rotation with the output shaft or member 22. The planet carriermember 20B is connected for common rotation with a seventh shaft orinterconnecting member 56 and an eighth shaft or interconnecting member58. The set of planet gears 20D are each configured to intermesh withboth the sun gear member 20A and the ring gear member 20C.

The input shaft or member 12 is continuously connected to an engine (notshown) or to a turbine of a torque converter (not shown). The outputshaft or member 22 is continuously connected with the final drive unitor transfer case (not shown).

The torque-transmitting mechanisms or the clutches 26, 28 and the brakes30, 32, 34 and 36 allow for selective interconnection of the shafts orinterconnecting members, members of the planetary gear sets and thehousing. For example, the first clutch 26 is selectively engageable toconnect the input shaft or member 12 with the seventh shaft orinterconnecting member 56 and the eighth shaft or interconnecting member58. The second clutch 28 is selectively engageable to connect the fourthshaft or interconnecting member 48 and the sixth shaft orinterconnecting member 54 with the seventh shaft or interconnectingmember 56 and the eighth shaft or interconnecting member 58. The firstbrake 30 is selectively engageable to connect the second and thirdshafts or interconnecting members 44 and 46 with a stationary element orthe transmission housing 50 in order to prevent members 44 and 46 fromrotating relative to the transmission housing 50. The second brake 32 isselectively engageable to connect the first shaft or interconnectingmember 42 with the stationary element or the transmission housing 50 inorder to prevent the first shaft or interconnecting member 42 fromrotating relative to the transmission housing 50. The third brake 34 isselectively engageable to connect the fifth shaft or interconnectingmember 52 and the ring gear 18C of the third planetary gear set 18 witha stationary element or the transmission housing 50 in order to preventthe fifth shaft or interconnecting member 52 and ring gear 18C fromrotating relative to the transmission housing 50. The fourth brake 36 isselectively engageable to connect the seventh and eighth shafts orinterconnecting members 56 and 58 with a stationary element or thetransmission housing 50 in order to prevent members 56 and 58 fromrotating relative to the transmission housing 50.

Referring now to FIGS. 2 and 3, the operation of the embodiment of theeight speed transmission 10 will be described. It will be appreciatedthat the transmission 10 is capable of transmitting torque from theinput shaft or member 12 to the output shaft or member 22 in at leasteight forward speed or torque ratios and at least one reverse speed ortorque ratio with a triple overdrive. Each forward and reverse speed ortorque ratio is attained by engagement of one or more of thetorque-transmitting mechanisms (i.e. first clutch 26, second clutch 28,first brake 30, second brake 32, third brake 34 and fourth brake 36), aswill be explained below. FIG. 3 is a truth table presenting the variouscombinations of torque-transmitting elements that are activated orengaged to achieve the various gear states. Actual numerical gear ratiosof the various gear states are also presented although it should beappreciated that these numerical values are exemplary only and that theymay be adjusted over significant ranges to accommodate variousapplications and operational criteria of the transmission 10. An exampleof the gear ratios that may be obtained using the embodiments of thepresent invention are also shown in FIG. 3. Of course, other gear ratiosare achievable depending on the gear diameter, gear teeth count and gearconfiguration selected.

To establish reverse gear, the second brake 32 and the fourth brake 36are engaged or activated. The second brake 32 connects the first shaftor interconnecting member 42 with the stationary element or thetransmission housing 50 in order to prevent the first shaft orinterconnecting member 42 from rotating relative to the transmissionhousing 50. The fourth brake 36 connects the seventh and eighth shaftsor interconnecting members 56 and 58 with a stationary element or thetransmission housing 50 in order to prevent members 56 and 58 fromrotating relative to the transmission housing 50. Likewise, the eightforward ratios are achieved through different combinations of clutch andbrake engagement, as shown in FIG. 3.

It will be appreciated that the foregoing explanation of operation andgear states of the eight speed transmission 10 assumes, first of all,that all the clutches and brakes not specifically referenced in a givengear state are inactive or disengaged and, second of all, that duringgear shifts, i.e., changes of gear state, between at least adjacent gearstates, a clutch or brake engaged or activated in both gear states willremain engaged or activated.

The description of the invention is merely exemplary in nature andvariations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A transmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having first, secondand third members; a first interconnecting member continuouslyinterconnecting the first member of the first planetary gear set withfirst member of the third planetary gear set; a second interconnectingmember continuously interconnecting the second member of the firstplanetary gear set with the second member of the second planetary gearset; a third interconnecting member continuously interconnecting thethird member of the first planetary gear set with the third member ofthe second planetary gear set; a fourth interconnecting membercontinuously interconnecting the first member of the second planetarygear set with the second member of the third planetary gear set; a fifthinterconnecting member continuously interconnecting the third member ofthe third planetary gear set with the first member of the fourthplanetary gear set; and six torque transmitting devices selectivelyengageable to interconnect one of the first, second, and third memberswith at least one other of the first members, second members, thirdmembers, and a stationary member, and wherein the torque transmittingdevices are selectively engageable in combinations of at least two toestablish at least eight forward speed ratios and at least one reversespeed ratio between the input member and the output member.
 2. Thetransmission of claim 1 wherein the first member of the first planetarygear set, the first member of the second planetary gear set, the firstmember of the third planetary gear set and the first member of thefourth planetary gear set are sun gears, the second member of the firstplanetary gear set, the second member of the second planetary gear set,the second member of the third planetary gear set and the second memberof the fourth planetary gear set are carrier members and the thirdmember of the first planetary gear set, third member of the secondplanetary gear set, the third member of the third planetary gear set andthe third member of the fourth planetary gear set are ring gears.
 3. Thetransmission of claim 1 wherein the input member is continuouslyinterconnected with the first member of the first planetary gear set andthe first member of the third planetary gear set and the output memberis continuously interconnected with the third member of the fourthplanetary gear set.
 4. The transmission of claim 1 wherein four of thesix torque transmitting devices are brakes and two of the six torquetransmitting devices are clutches.
 5. The transmission of claim 1wherein the stationary member is a transmission housing.
 6. Thetransmission of claim 1 wherein a first of the six torque transmittingdevices is selectively engageable to interconnect the input member,first member of the first planetary gear set and the first member of thethird planetary gear set with the second member of the fourth planetarygear set.
 7. The transmission of claim 6 wherein a second of the sixtorque transmitting devices is selectively engageable to interconnectthe first member of the second planetary gear set and the second memberof the third planetary gear set with the second member of the fourthplanetary gear set.
 8. The transmission of claim 7 wherein a third ofthe six torque transmitting devices is selectively engageable tointerconnect the second member of the first planetary gear set andsecond member of the second planetary gear set with the stationarymember.
 9. The transmission of claim 8 wherein a fourth of the sixtorque transmitting devices is selectively engageable to interconnectthe third member of the first planetary gear set and the third member ofthe second planetary gear set with the stationary member.
 10. Thetransmission of claim 9 wherein a fifth of the six torque transmittingdevices is selectively engageable to interconnect the third member ofthe third planetary gear set and the first member of the fourthplanetary gear set with the stationary member.
 11. The transmission ofclaim 10 wherein a sixth of the six torque transmitting devices isselectively engageable to interconnect the second member of the fourthplanetary gear set with the stationary member.
 12. A transmissioncomprising: an input member; an output member; first, second, third andfourth planetary gear sets each having first, second and third members,wherein the input member is continuously interconnected with the firstmember of the first planetary gear set and the first member of the thirdplanetary gear set and the output member is continuously interconnectedwith the third member of the fourth planetary gear set; a firstinterconnecting member continuously interconnecting the first member ofthe first planetary gear set with first member of the third planetarygear set; a second interconnecting member continuously interconnectingthe second member of the first planetary gear set with the second memberof the second planetary gear set; a third interconnecting membercontinuously interconnecting the third member of the first planetarygear set with the third member of the second planetary gear set; afourth interconnecting member continuously interconnecting the firstmember of the second planetary gear set with the second member of thethird planetary gear set; a fifth interconnecting member continuouslyinterconnecting the third member of the third planetary gear set withthe first member of the fourth planetary gear set; a first torquetransmitting device selectively engageable to interconnect the inputmember, first member of the first planetary gear set and the firstmember of the third planetary gear set with the second member of thefourth planetary gear set; a second torque transmitting deviceselectively engageable to interconnect the first member of the secondplanetary gear set and the second member of the third planetary gear setwith the second member of the fourth planetary gear set; a third torquetransmitting device selectively engageable to interconnect the secondmember of the first planetary gear set and second member of the secondplanetary gear set with the stationary member; a fourth torquetransmitting device selectively engageable to interconnect the thirdmember of the first planetary gear set and the third member of thesecond planetary gear set with the stationary member; a fifth torquetransmitting device selectively engageable to interconnect the thirdmember of the third planetary gear set and the first member of thefourth planetary gear set with the stationary member; and a sixth torquetransmitting device selectively engageable to interconnect the secondmember of the fourth planetary gear set with the stationary member, andwherein the torque transmitting devices are selectively engageable incombinations of at least two to establish at least eight forward speedratios and at least one reverse speed ratio between the input member andthe output member.
 13. The transmission of claim 12 wherein the firstmember of the first planetary gear set, the first member of the secondplanetary gear set, the first member of the third planetary gear set andthe first member of the fourth planetary gear set are sun gears, thesecond member of the first planetary gear set, the second member of thesecond planetary gear set, the second member of the third planetary gearset and the second member of the fourth planetary gear set are carriermembers and the third member of the first planetary gear set, thirdmember of the second planetary gear set, the third member of the thirdplanetary gear set and the third member of the fourth planetary gear setare ring gears.
 14. The transmission of claim 12 wherein the stationarymember is a transmission housing.
 15. A transmission comprising: aninput member; an output member; first, second, third and fourthplanetary gear sets each having a sun gear, a carrier member and a ringgear, wherein the input member is continuously interconnected with thesun gear of the first planetary gear set and the sun gear of the thirdplanetary gear set and the output member is continuously interconnectedwith the ring gear of the fourth planetary gear set; a firstinterconnecting member continuously interconnecting the sun gear of thefirst planetary gear set with sun gear of the third planetary gear set;a second interconnecting member continuously interconnecting the carriermember of the first planetary gear set with the carrier member of thesecond planetary gear set; a third interconnecting member continuouslyinterconnecting the ring gear of the first planetary gear set with thering gear of the second planetary gear set; a fourth interconnectingmember continuously interconnecting the sun gear of the second planetarygear set with the carrier member of the third planetary gear set; afifth interconnecting member continuously interconnecting the ring gearof the third planetary gear set with the sun gear of the fourthplanetary gear set; a first torque transmitting device selectivelyengageable to interconnect the input member, sun gear of the firstplanetary gear set and the sun gear of the third planetary gear set withthe carrier member of the fourth planetary gear set; a second torquetransmitting device selectively engageable to interconnect the sun gearof the second planetary gear set and the carrier member of the thirdplanetary gear set with the carrier member of the fourth planetary gearset; a third torque transmitting device selectively engageable tointerconnect the carrier member of the first planetary gear set andcarrier member of the second planetary gear set with the stationarymember; a fourth torque transmitting device selectively engageable tointerconnect the ring gear of the first planetary gear set and the ringgear of the second planetary gear set with the stationary member; afifth torque transmitting device selectively engageable to interconnectthe ring gear of the third planetary gear set and the sun of the fourthplanetary gear set with the stationary member; and a sixth torquetransmitting device selectively engageable to interconnect the carriermember of the fourth planetary gear set with the stationary member, andwherein the torque transmitting devices are selectively engageable incombinations of at least two to establish at least eight forward speedratios and at least one reverse speed ratio between the input member andthe output member.
 16. The transmission of claim 15 wherein thestationary member is a transmission housing.